1. Field of the Invention
The present invention relates to an exhaust valve capable of rapidly discharging, e.g., either a fluid in a cylinder or compressed air in a pneumatic tank therefrom.
2. Description of the Related Art
FIG. 1 shows a conventional exhaust valve. An exhaust valve 2 comprises a first body 4 and a second body 6. The first body 4 has first and second ports 8, 10 defined therein, which have screw threads respectively, and a hole 12 which communicates with the first and second ports 8, 10. The second body 6 has a third port 14 which is defined therein and has a screw thread, and a hole 16 which is defined in the leading end 18 of the second body 6 and communicates with the third port 14. A lip packing 22 having a sleeve 20 is disposed in the bottom of the hole 12 of the first body 4, and the second body 6 is fitted in the bottom thereof.
When a fluid is supplied from the first port 8, the exhaust valve 2 constructed in the above-described manner is actuated to displace the lip packing 22 in the direction indicated by the arrow A so as to be seated on the leading end 18 of the second body 6, thereby cutting off the communication between the hole 16 of the second body 6 and the hole 12 of the first body 4. Further, the sleeve 20 of the lip packing 22 is reduced in diameter by the pressure of the fluid supplied from the first port 8 so as to be opened, i.e., make a communication state, thereby making it possible to supply the fluid supplied from the first port 8 to the second port 10. When, on the other hand, the supply of the fluid from the first port 8 is stopped and the fluid is supplied from the second port 10, the pressure of the fluid acts on the sleeve 20 of the lip packing 22, that is, the outer diameter of the sleeve 20 increases so as to bring a peripheral edge of the sleeve 20 into abutment against an inner wall portion for defining the hole 12 in the first body 4, thereby separating the lip packing 22 from the leading end 18. Thus, the fluid supplied from the second port 10 is supplied via the hole 16 of the second body 6 to the third port 14.
When it is desired to dispose the exhaust valve 2 constructed as described above to a pipe coupled to a cylinder or the like, the first and second ports 8, 10 are connected to a fluid feed source and the cylinder respectively, and the third port 14 is open to the atmosphere. When the fluid is supplied to the cylinder under this connection, it flows into the second port 10 from the first port 8. When the fluid is discharged from the cylinder, it flows into the third port 14 from the second port 10 so as to be discharged into the atmosphere.
By disposing the exhaust valve 2 in the pipe coupled to the cylinder in the above-described manner, the a piping distance to an exhaust portion from which the fluid is exhausted can be reduced, thereby making it possible to quickly discharge the fluid and improve the response characteristic of the cylinder. Since the piping distance to the exhaust portion can be reduced, portions or ranges to which water or moisture adheres, can be reduced to a minimum.
However, the second port 10, when it communicates with a device such as the cylinder or the like to thereby supply the fluid to the cylinder and discharge it therefrom, is disposed at a right angle to the first port 8. Therefore, a pipe is limited to a so-called L-shaped line or tube. Thus, when the exhaust valve 2 is connected to a linearly pipe-arranged portion, a change in a piping direction should be carried out. The piping direction to the third port 14 is also restricted. Further, when a non-metallic member such as vinyl is used as a pipe, it cannot be connected to each of the first through third ports 8, 10, 14 which have been formed so as to be connected with a corresponding object by screw threads, and a connecting process becomes cumbersome.